1. Field of the Invention
The invention relates to a device for cutting vertical paper sheets and, more particularly, for cutting a web of paper in a printer.
2. The Prior Art
In the case of paper being discharged from printers, both individual forms and endless paper webs pass through the printers. Here endless paper is being used, it is necessary to cut the paper off after it has been printed and eject the sheets onto a place of deposit. Sheet cutting is carried out automatically in these systems by means of a cutting wheel which moves on a carriage against a stationary cutting edge. Cutters of this type are described in German GM No. 7812759 and U.S. Pat. No. 4,152,963, corresponding to German OS No. 2655832. The devices disclosed in these publications generally comprise carriage driven stepped rolls of which the larger portions serve to shear or tear paper along the cutting edges. Pressure rolls serve to retain the paper against the cutting edge during cutting. These devices do not include guide surfaces for positioning of the paper being fed and cut in the cutter.
One drawback with known cutter arrangements is in the guidance of paper through the cutter device. Usually a printer used both for printing endless paper and for printing individual forms has different paper delivery guides for the respective modes. In practice, the different paper guides are switched into operating position depending on the particular mode. This requires an additional control mechanism. Also, a gap is necessary between the cutting edge and the beginning of the delivery guide walls through which the cutting wheel or cutting knife can be conducted. This gap may disrupt smooth passage of the paper through the cutter device.
A further drawback in known cutter arrangements is that delivery guide walls, which open onto a paper deposit, do not precisely direct movement of the paper and may extend along a very small angle with respect to the cutting edge. Thus, there is no tensioning of the paper sheet about to be cut so as to be particularly undesirable when cutting thin or perforated paper.